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yap-6.3/os/pl-table.c
2013-11-15 01:10:25 +00:00

474 lines
9.8 KiB
C

/* Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@vu.nl
WWW: http://www.swi-prolog.org
Copyright (C): 1985-2012, University of Amsterdam
VU University Amsterdam
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/*#define O_DEBUG 1*/
#include "pl-incl.h"
#ifdef O_PLMT
#define LOCK_TABLE(t) if ( t->mutex ) simpleMutexLock(t->mutex)
#define UNLOCK_TABLE(t) if ( t->mutex ) simpleMutexUnlock(t->mutex)
#else
#define LOCK_TABLE(t) (void)0
#define UNLOCK_TABLE(t) (void)0
#endif
static inline Symbol rawAdvanceTableEnum(TableEnum e);
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
This file provides generic hash-tables. Most of the implementation is
rather straightforward. Special are the *TableEnum() functions to
create, advance over and destroy enumerator objects. These objects are
used to enumerate the symbols of these tables, used primarily for the
pl_current_* predicates.
The enumerators cause two things: (1) as long as enumerators are
associated, the table will not be rehashed and (2) if symbols are
deleted that are referenced by an enumerator, the enumerator is
automatically advanced to the next free symbol. This, in general, makes
the enumeration of hash-tables safe.
TBD: Resizing hash-tables causes major headaches for concurrent access.
We can avoid this by using a dynamic array for the list of hash-entries.
Ongoing work in the RDF store shows hash-tables that can handle
concurrent lock-free access.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
static Symbol *
allocHTableEntries(int buckets)
{ size_t bytes = buckets * sizeof(Symbol);
Symbol *p;
p = allocHeapOrHalt(bytes);
memset(p, 0, bytes);
return p;
}
Table
newHTable(int buckets)
{ Table ht;
ht = allocHeapOrHalt(sizeof(struct table));
ht->buckets = (buckets & ~TABLE_MASK);
ht->size = 0;
ht->enumerators = NULL;
ht->free_symbol = NULL;
ht->copy_symbol = NULL;
#ifdef O_PLMT
if ( (buckets & TABLE_UNLOCKED) )
ht->mutex = NULL;
else
{ ht->mutex = allocHeapOrHalt(sizeof(simpleMutex));
simpleMutexInit(ht->mutex);
}
#endif
ht->entries = allocHTableEntries(ht->buckets);
return ht;
}
void
destroyHTable(Table ht)
{
#ifdef O_PLMT
if ( ht->mutex )
{ simpleMutexDelete(ht->mutex);
freeHeap(ht->mutex, sizeof(*ht->mutex));
ht->mutex = NULL;
}
#endif
clearHTable(ht);
freeHeap(ht->entries, ht->buckets * sizeof(Symbol));
freeHeap(ht, sizeof(struct table));
}
#if O_DEBUG
static int lookups;
static int cmps;
int
exitTables(int status, void *arg)
{ (void)status;
(void)arg;
Sdprintf("hashstat: Anonymous tables: %d lookups using %d compares\n",
lookups, cmps);
return 0;
}
#endif
void
initTables(void)
{ static int done = FALSE;
if ( !done )
{ done = TRUE;
DEBUG(MSG_HASH_STAT, PL_on_halt(exitTables, NULL));
}
}
Symbol
lookupHTable(Table ht, void *name)
{ Symbol s = ht->entries[pointerHashValue(name, ht->buckets)];
DEBUG(MSG_HASH_STAT, lookups++);
for( ; s; s = s->next)
{ DEBUG(MSG_HASH_STAT, cmps++);
if ( s->name == name )
return s;
}
return NULL;
}
#ifdef O_DEBUG
void
checkHTable(Table ht)
{ int i;
int n = 0;
for(i=0; i<ht->buckets; i++)
{ Symbol s;
for(s=ht->entries[i]; s; s=s->next)
{ assert(lookupHTable(ht, s->name) == s);
n++;
}
}
assert(n == ht->size);
}
#endif
/* MT: Locked by calling addHTable()
*/
static Symbol
rehashHTable(Table ht, Symbol map)
{ Symbol *newentries, *oldentries;
int newbuckets, oldbuckets;
int i;
#if P_PLMT
int safe_copy = (ht->mutex != NULL);
#else
int safe_copy = TRUE;
#endif
newbuckets = ht->buckets*2;
newentries = allocHTableEntries(newbuckets);
DEBUG(MSG_HASH_STAT,
Sdprintf("Rehashing table %p to %d entries\n", ht, ht->buckets));
for(i=0; i<ht->buckets; i++)
{ Symbol s, n;
if ( safe_copy )
{ for(s=ht->entries[i]; s; s = n)
{ int v = (int)pointerHashValue(s->name, newbuckets);
Symbol s2 = allocHeapOrHalt(sizeof(*s2));
n = s->next;
if ( s == map )
map = s2;
*s2 = *s;
s2->next = newentries[v];
newentries[v] = s2;
}
} else
{ for(s=ht->entries[i]; s; s = n)
{ int v = (int)pointerHashValue(s->name, newbuckets);
n = s->next;
s->next = newentries[v];
newentries[v] = s;
}
}
}
oldentries = ht->entries;
oldbuckets = ht->buckets;
ht->entries = newentries;
ht->buckets = newbuckets;
if ( safe_copy )
{ /* Here we should be waiting until */
/* active lookup are finished */
for(i=0; i<oldbuckets; i++)
{ Symbol s, n;
for(s=oldentries[i]; s; s = n)
{ n = s->next;
s->next = NULL; /* that causes old readers to stop */
freeHeap(s, sizeof(*s));
}
}
}
freeHeap(oldentries, oldbuckets * sizeof(Symbol));
DEBUG(CHK_SECURE, checkHTable(ht));
return map;
}
Symbol
addHTable(Table ht, void *name, void *value)
{ Symbol s;
int v;
LOCK_TABLE(ht);
v = (int)pointerHashValue(name, ht->buckets);
if ( lookupHTable(ht, name) )
{ UNLOCK_TABLE(ht);
return NULL;
}
s = allocHeapOrHalt(sizeof(struct symbol));
s->name = name;
s->value = value;
s->next = ht->entries[v];
ht->entries[v] = s;
ht->size++;
DEBUG(9, Sdprintf("addHTable(0x%x, 0x%x, 0x%x) --> size = %d\n",
ht, name, value, ht->size));
if ( ht->buckets * 2 < ht->size && !ht->enumerators )
s = rehashHTable(ht, s);
UNLOCK_TABLE(ht);
DEBUG(1, checkHTable(ht));
return s;
}
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Note: s must be in the table!
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
void
deleteSymbolHTable(Table ht, Symbol s)
{ int v;
Symbol *h;
TableEnum e;
LOCK_TABLE(ht);
v = (int)pointerHashValue(s->name, ht->buckets);
h = &ht->entries[v];
for( e=ht->enumerators; e; e = e->next )
{ if ( e->current == s )
rawAdvanceTableEnum(e);
}
for( ; *h; h = &(*h)->next )
{ if ( *h == s )
{ *h = (*h)->next;
s->next = NULL; /* force crash */
s->name = NULL;
s->value = NULL;
freeHeap(s, sizeof(struct symbol));
ht->size--;
break;
}
}
UNLOCK_TABLE(ht);
}
void
clearHTable(Table ht)
{ int n;
TableEnum e;
LOCK_TABLE(ht);
for( e=ht->enumerators; e; e = e->next )
{ e->current = NULL;
e->key = ht->buckets;
}
for(n=0; n < ht->buckets; n++)
{ Symbol s, q;
for(s = ht->entries[n]; s; s = q)
{ q = s->next;
if ( ht->free_symbol )
(*ht->free_symbol)(s);
freeHeap(s, sizeof(struct symbol));
}
ht->entries[n] = NULL;
}
ht->size = 0;
UNLOCK_TABLE(ht);
}
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Table copyHTable(Table org)
Make a copy of a hash-table. This is used to realise the copy-on-write
as defined by SharedTable. The table is copied to have exactly the
same dimensions as the original. If the copy_symbol function is
provided, it is called to allow duplicating the symbols name or value
fields.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
Table
copyHTable(Table org)
{ Table ht;
int n;
ht = allocHeapOrHalt(sizeof(struct table));
LOCK_TABLE(org);
*ht = *org; /* copy all attributes */
#ifdef O_PLMT
ht->mutex = NULL;
#endif
ht->entries = allocHTableEntries(ht->buckets);
for(n=0; n < ht->buckets; n++)
{ Symbol s, *q;
q = &ht->entries[n];
for(s = org->entries[n]; s; s = s->next)
{ Symbol s2 = allocHeapOrHalt(sizeof(*s2));
*q = s2;
q = &s2->next;
s2->name = s->name;
s2->value = s->value;
if ( ht->copy_symbol )
(*ht->copy_symbol)(s2);
}
*q = NULL;
}
#ifdef O_PLMT
if ( org->mutex )
{ ht->mutex = allocHeapOrHalt(sizeof(simpleMutex));
simpleMutexInit(ht->mutex);
}
#endif
UNLOCK_TABLE(org);
return ht;
}
/*******************************
* ENUMERATING *
*******************************/
TableEnum
newTableEnum(Table ht)
{ TableEnum e = allocHeapOrHalt(sizeof(struct table_enum));
Symbol n;
LOCK_TABLE(ht);
e->table = ht;
e->key = 0;
e->next = ht->enumerators;
ht->enumerators = e;
n = ht->entries[0];
while(!n && ++e->key < ht->buckets)
n=ht->entries[e->key];
e->current = n;
UNLOCK_TABLE(ht);
return e;
}
void
freeTableEnum(TableEnum e)
{ TableEnum *ep;
Table ht;
if ( !e )
return;
ht = e->table;
LOCK_TABLE(ht);
for( ep=&ht->enumerators; *ep ; ep = &(*ep)->next )
{ if ( *ep == e )
{ *ep = (*ep)->next;
freeHeap(e, sizeof(*e));
break;
}
}
UNLOCK_TABLE(ht);
}
static inline Symbol
rawAdvanceTableEnum(TableEnum e)
{ Symbol s, n;
Table ht = e->table;
if ( !(s = e->current) )
return s;
n = s->next;
while(!n)
{ if ( ++e->key >= ht->buckets )
{ e->current = NULL;
return s;
}
n=ht->entries[e->key];
}
e->current = n;
return s;
}
Symbol
advanceTableEnum(TableEnum e)
{ Symbol s;
#ifdef O_PLMT
Table ht = e->table;
#endif
LOCK_TABLE(ht);
s = rawAdvanceTableEnum(e);
UNLOCK_TABLE(ht);
return s;
}